Efficient material handling is essential to competitive manufacturing. In warehouse storage facilities, reducing the amount of square footage required to store material and increasing accessibility to stored material reduces overhead cost and increases manufacturing thruput. The result is increased profit for the manufacturer.
Previous inventions, such as U.S. Pat. Nos. 4,341,313, Doring; 5,141,118, Gay; 4,687,404, Seiz; and 5,180,069, Krummell, disclose inventions which attempt to utilize warehouse storage more efficiently. These inventions generally disclose warehouse storage systems comprising a plurality of bays. Each bay contains a series of nested carts which roll along a series of rails. When no material is being stored, the carts reside on top of one another at a position close to a user. Material is placed on a first cart and then the cart is "pushed back" along two rails to a rearward position exposing the next cart. The rails are inclined toward the user to allow the carts to roll to a position toward the front of the bay, closest to the user. This allows easy access to stored material when retrieval is desired.
However, the use of the above warehouse storage facilities creates some difficulties. First, because the carts disclosed in these inventions are bulky and have a fixed geometry, they cannot easily be removed from the storage facility and replaced.
Second, since the carts bridge across both rails, the cart's position along each rail cannot be adjusted independent of the other rail. This lack of independent adjustment can limit the types of unique material configurations for which the cart can store. Also, a forklift placing material on a pushback which is not oriented parallel to the drives causes more force to be applied to one drive than another. If the drives are independent of one another, one drive can give more due to the increased force than the other.
Third, because of the stacked configuration, the length of the prior art pushbacks are limited. The length of the prior art pushbacks are based on the amount of pushbacks which can be stacked on top of one another. The more available height, the more rectangular sections can be stacked which means the more available length of the pushback.
Lastly, because of the cart's rigidity and type of engagement to the rails, the carts are able only to follow linear rails. They are not able to bend or move along a curved surface when being pushed back. This restriction can limit areas where the warehouse storage unit is located and surfaces on which it is placed. The present invention was designed in light of these drawbacks.